The present invention relates to the art of fluid operated linear actuator control systems and in particular such a control system for a drive arrangement of the type wherein two fluid operated linear actuators act upon a shaft at an angle with respect to each other for causing rotation thereof. Such a drive arrangement is disclosed in commonly assigned U.S. patent application Ser. No. 660,114, filed Feb. 23, 1976 by John T. Mazur, and entitled "Rotational Positioning Using Linear Actuators" and the substance of this application is incorporated herein by reference to the extent necessary for a complete understanding of the present invention.
As is pointed out in the afore-noted application, a variety of different arts require the use of a steerable mount to provide rotational positioning of a workpiece, instrument, or other device, such as in radio communications wherein antennas are mounted so as to be steerable through a wide range of arcs. In particular, an advantageous drive arrangement is formed wherein two fluid operated linear actuators act upon a shaft at an angle with respect to each other for causing rotation of the shaft so as to produce the desired rotational positioning as required. Furthermore, the efficiency of operation of such drive arrangements is enhanced when the linear actuators are free to expand or contract without resistance, when deactivated, since any excess resistance to the motion of the inactive actuator will detract from the driving force of the active atuator.
However, in order to produce a drive arrangement which is efficient, reliable, and easy to construct, at a reasonable cost, it is necessary that a fluid control system be developed that is not very complex.
It is therefore an object of the present invention to provide a fluid control system for a drive arrangement of the aforementioned type which is able to power a first linear actuator while rendering inactive a second co-acting linear actuator in a manner that causes the second actuator to offer a minimum of resistance to the force applied by the first actuator.
It is another object of the present invention to provide a control system of reduced complexity and high reliability and efficiency.
These and other objects and advantages of the present invention will become more readily apparent from the following description of a preferred embodiment when viewed in conjunction with the accompanying drawings which are a part hereof.